According to the catastrophe-modeling
and weather-risk management firm AIR Worldwide Corporation, New
York City is the American city at second highest risk for
potential total economic loss from nearly worst-case
hurricane scenarios, preceded only by the Miami/Fort Lauderdale
area of Florida. In the wake of the damaging storms along the
Gulf Coast, it’s important to consider whether proper
measures are being taken to see that the tragedy unfolding
in and around the Big Easy does not also occur in other metropolitan
areas, whether or not climate change is driving the increase
in the ferocity of hurricanes and other devastating weather
events.

A History of Tumultuous Weather

New York City has a long history
of turbulent weather and consequent damage from major tropical
storms and hurricanes during the summer and early fall. A few
of the most damaging storms include:

The Hurricane of 1821, which produced a sea level rise of
up to 13 feet (about 4 meters) in one hour in the area that
is now Battery Park City.

The “West
Indian monster” of 1893, which triggered a 30-foot
(about 9-meter) storm surge that razed nearly all man-made
structures on its course through southern Brooklyn and
Queens.

The "1938
Long Island Express” and its accompanying tidal
surge and surf, which registered on seismographs in Alaska
when it roared ashore at Bayport, Long Island, causing
690 deaths across the Northeast.

National
Oceanic and Atmospheric Administration, Department of Commerce — Waves
thrashing a seawall along the New England coast in 1938 storm.

Tropical
Storm Floyd in September 1999, during which New York
State and upstate New Jersey received 10 to 15 inches (25-38
centimeters) of rain during a 24-hour period, causing significant
flash flooding in New York City. The New York metropolitan
transportation system nearly shut down and emergency storm
shelters opened throughout the city.

National
Oceanic and Atmospheric Administration, National Climatic
Data Center — Tropical Storm Floyd makes its way
into New England on September 16, 1999.

Devastating northeasters can also cause significant damage
to New York City; in addition, overall damage can be even more
widespread than for hurricanes, sometimes extending along the
entire East Coast. Northeasters are
cyclonic storms that begin as low-pressure systems off the mid-Atlantic
coast and ravage the Northeast as they move up the coast during
the fall, winter, and early spring. Despite their winds being
weaker than those of hurricanes, they inflict heavy damages because
they often maintain their strength over several tidal cycles
at a particular location. Among the most damaging northeasters
have been:

NYC
Office of Emergency Management — Madison Avenue and
50th Street in New York City during the Blizzard of 1888.

The Blizzard
of 1888, in which 40 inches (about 102 centimeters)
of snow fell in New York City and approximately 400 people
died. The northeaster affected the East Coast from Chesapeake
Bay to Maine.

The northeaster of December 1992, which prompted the closing of New
York City’s airports, trains, subways, and highways;
caused significant beach and dune erosion; and collapsed
a row of houses on Fire Island’s western side.

University of Illinois WW2010 Project — Infrared
satellite image of March 1993 northeaster.

Global Warming Increases the Potential
for Dramatic Weather Events

Despite a history of tumultuous weather, climate scientists
warn that New York City’s earlier weather patterns and
current climate may pale in comparison to the possible onslaught
of weather-related changes being brought about by global warming,
including increased temperatures and higher precipitation levels.
According to the regional climate change assessment for the Metro
East Coast (“The Potential Impacts of Global Warming on
the Metropolitan East Coast,” findings included in the U.S.
Global Change Research Program’sNational
Assessment of the Potential Consequences of Climate Variability
and Change), the minimum and maximum temperatures in
New York City have shown a long-term warming trend during the
past century, each rising by approximately 4°F (about 2.2°C)
since 1880. Global climate models project that the region’s
temperatures could increase by about 1°-4°F (about 0.6°-2.2°C)
by 2030 and by about 5°-10°F (about 2.8°-5.6°C)
by 2100. Furthermore, projections summarized by the Intergovernmental
Panel on Climate Change estimate a 10%-20% increase
in precipitation by 2100 (with a range of 0%-40%), with less
change in the spring and more in the winter.

Destructive Weather’s Potential
Impact on the New York Metropolitan Region

Scientists have identified a broad range of possible storm-related
impacts on the New York metropolitan area that could result from
global warming, including sea level rise, increased storm surge,
coastal and inland flooding, coastal erosion, and the loss of
wetlands. More intense hurricanes and northeasters are also expected
to have devastating effects on the region’s infrastructure,
including its transportation systems.

One impact of climate change that has the potential to have
profound effects on the New York metropolitan area is sea level
rise. Sea level rise is not a new phenomenon, as global sea levels
have been rising since the 19th century, although at a relatively
small rate compared to projections of future rates of rise. By
raising the temperature of the oceans, thus increasing their
volume since water expands when it’s heated, and melting
land-based glaciers and sections of ice sheets in West Antarctica,
East Antarctica, and Greenland, global
warming will cause the rate of sea level rise to increase significantly.
Observations summarized by the Intergovernmental Panel on Climate
Change indicate that global
sea level increased 6-8 inches (15-20 centimeters) during
the 20th century; this
rate was roughly ten times greater than the average rate of rise
over the preceding 2000 years. The relative
rate of sea level rise in the region is currently about 9-15
inches (23-38 centimeters) per century, because geologic subsidence
in the region causes the New York metropolitan area’s sea
level to rise more quickly than the increase measured in most
other areas of the United States and the world. It is estimated
that the region’s
ocean levels may rise roughly another 4-12
inches (10-30 centimeters) over the next 15 years, 7-24 inches
(18-61 centimeters) by the 2050s, and 9-43 inches (23-109 centimeters)
by the 2080s.

United
States Department of the Interior, United States Geological Survey — Map
of the Atlantic seaboard shows the coast’s
relative vulnerability to sea level rise.

The numerous consequences of sea level rise, including
higher storm surge, more frequent flooding, increased beach erosion,
and ultimately the loss of low-lying areas and coastal wetlands,
could result in very serious economic and environmental impacts
for the New York metropolitan area.

Another threat to New York City’s citizens and property
during an extreme weather event is storm surge, which is the
cause of approximately 90% of all deaths and injuries associated
with hurricanes in the United States. Storm
surge is produced when a huge dome of water is pushed towards
the shore by a hurricane’s surface winds and low barometric
pressure. Since its height is augmented by a rise in sea level,
rising seas due to global warming can trigger significantly greater
damage (especially because the maximum height of storm waves
increases by 50% more than the amount of sea level rise). New
York City’s geographic location also amplifies the effects
of this phenomenon. The New York Bight, the sharp bend in
the Atlantic coastline where New York and New Jersey converge,
intensifies the storm surge associated with even a moderate hurricane,
resulting in a larger
area of destruction and flooding.

United
States Department of the Interior, United States Geological
Survey — New York Bight.

National
Oceanic and Atmospheric Administration, National Weather Service — Category
2 hurricane storm surge simulation at the Brooklyn Battery
Tunnel in New York City.

Coastal and inland flooding is another potentially serious
consequence that will be amplified by sea level rise and higher
storm surges. As the ocean’s level rises, the flooding
generated by extreme weather events is likely to damage larger
areas. The New York metropolitan area’s coastline is highly
developed, placing a rapidly growing population and a tremendous
amount of private property and public infrastructure at enormous
risk of flooding. Much
of the region’s population is concentrated
near the shore, with coastal populations in New York, New
Jersey, and Connecticut expanding by approximately 17% between
1960 and 1995. Population
growth in seven coastal counties in the region has exceeded
100% during the last few decades, as cited in the Climate
Change Information Resources for the New York Metropolitan Region,
a by-product of the Metropolitan East Coast
Assessment.

U.S.
Army Corps of Engineers — A northeaster in October 1991
generates flooding on the shore of Monmouth Beach, New Jersey.

Gornitz, Sea Level Rise and Coasts, in Metropolitan East Coast Assessment:
Climate Change and a Global City, 2001 —
Coney Island population
and property at risk from flooding and
sea-level rise.
[Click on image to
see larger version]

NYC
Office of Emergency Management — Flooded PATH station in
December 1992.

bridges that connect them with the region’s
suburbs and outer counties are critical
to transit in the area. After the December 1992 northeaster,
which disrupted commuter transit between New York City and New
Jersey for ten days, floodgates were installed at the top of
stairways leading down to subway stations and a decision was
made that the building of any new entrances must allow for current
flood levels.

NYC
Office of Emergency Management — Shaded area represents
the potential height of floods from a Category 2 hurricane at
South Ferry (Battery) subway station.

Concern about considerable loss of life arises because there
are likely to be significant problems associated with evacuating
New York City in the lead-up to extreme storms. Evacuation
of the high-density regions near the flood-prone coastline would
be extremely difficult because many evacuation routes, including
both roads and public transportation, extend through areas that
may be inundated with water. In addition, because many of the
bridges connecting Manhattan to the mainland are elevated, they
would respond to the wind effects of an approaching storm well
before such winds would be felt at ground level. As a result,
their use as evacuation routes would have to be restricted well
before roads at ground level, further complicating an evacuation.
The problem of unusable evacuation routes is compounded by the
fact that, as of 2001, only 50% of households in New York City
and 20% of households in Manhattan had access to their own vehicles,
which would mean that a large percentage of the city’s
population would need to be evacuated using potentially
compromised public transportation systems.

As evidence of the link between climate change and the intensification
of hurricanes and northeasters continues to mount, it is important
to identify those areas at greatest risk for consequential damage
to the environment, and loss of life and property. Substantial
data suggest that, should an extreme storm strike, especially
during times of high tide, the New York metropolitan area is
likely to suffer significant damage and loss of life. Although
global warming’s effect on storm severity is not yet perfectly
understood, the risk to New York City is already significant,
and global warming will only make the situation worse. Recognizing
this, greater consideration needs to be given to reducing
both the near-term and increasing long-term risks.

* Special thanks to NASA GISS; Hunter College, CUNY; and CIESIN
for use of their pictures.